An auger is a drilling device used in construction to dig holes in the ground for structures such as posts, columns and foundation piles. An auger may be attached to a mobile excavator such as a tractor or a specifically designed drilling rig. An auger is typically driven by a drive mechanism that includes a hydraulic motor and gearbox.
During a drilling cycle, an auger rotates and removes material from the hole being drilled. The auger is then lifted out of the hole and flicked between forward and reverse rotation in order to dislodge the drillings (e.g. earth, rock). The auger is then put back down the hole and into steady rotation to remove further material. When drilling foundations it is common for the auger to come into contact with rock or other hard materials that can either stop the rotation or cause vibration and intermittent loading on the drive mechanism. This can create excessive loading on the gears and motor.
Furthermore, if the auger is stopped or reversed abruptly, the drill will exert a high inertia load on the drilling mechanism. If these inertia loads are not controlled, the hydraulic motor may overrun and cause damage to the drive mechanism.
It would be desirable to absorb shock loading from the drilling operation and inertia loads when the drilling mechanism is suddenly stopped or reversed without damage.
Other advantages of the present invention will become apparent from the following description, taken in connection with the accompanying drawings, wherein, by way of illustration and example, preferred embodiments of the present invention are disclosed.